Constant current transformer



Jan. 24, 1933. o. A. PEARSON ET AL CONSTANT CURRENT TRANSFORMER FiledFeb. 19, 1951 a. Lama AA INVENTdRS ATTORNEYS Patented 10.11.24, 1933.

or primary section of the transformer core UNITED STATES. PATENT orrrcsOSCAR A. PEARSON, OI OAK. PARK, AND CHESTER H. THORDARSON, OI CHICAGO,

ILLINOIS, ASSIGNOES TO THOEDABSON ELECTRIC MANUFACTURING COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS CONSTANT CURRENTTRANSFORMER ap lication died February 19, 1931. Serial 110. 516,858

A further feature of the invention relates to the method of controllingthe leakage characteristics of a transformer in accordance with thesecondary load.

A further feature of the invention relates to a constant currenttransformer of the shell type having'a core which is easily assembled.

Another feature relates to the shell type of constant currenttransformer provided wlth magnetic shunts completely surrounded by thecore, which shunts are integrally united to the core.

Another feature of the invention relates to a constantcurrenttransformer employing a plurality of coil sections whicharesym'xnetncally disposed about a common primary core and arerovidedwith magnetic shunts for maintaining the secondary currentsubstantially constant, I

A still further feature relatesto the novel organization and arrangementof elements which go to make up a cheap, eficient and easily assembledconstant current transformer wherein the magnetic efiects of the coilW1i1Cl ings are balanced.

In the single figure of the drawing, which shows a longitudinal sectionof the transformer, the numeral. 1 represents a pile-up of straightlaminations constituting the main The numeral 2 represents a windingwhich surrounds the core portion 1, preferably at its center.Anysuitable design of coil winding may be utilized, In the case ofconstant current high duty transformers it is preferred to employ aso-called ribbon winding for this purpose. The winding 2 is of courseinsulated by a suitable insulating spool 3 from the core portion 1. Itwill he assumed for the present that the coil 2 constitutes the primarywinding of the transformer, and if desired this coil may be providedwith 'suit able taps. The secondary winding or windingsare representedin the drawing by the numerals 4 and 5 and are dis osed symmetricallyabout the core 1, pre erably at equal distances from the primary winding2. The secondary windings 4 and 5 are insulated from the core 1 in anysuitable manner, for example by being wound upon insulating spools 6.

For the purpose of completing the main ma netic circuit for the primaryand secon ar windings there are provided two pileu s o laminations. Thelaminations of each 0 these latter sets comprises a portion 7 extendingparallel to the main core portion 1, and end. or 1e portions 8 and 9adapted to butt against the core portion 1, as shown in the drawing.Integrally formed with each of these laminations are two intermediateleg portions 10 and 11 which are slightly shorter than the leg portions8 and 9, thus providing two gaps 12,- 13 on each side of the coreportion 1. The legs 10 and 11 are preferably narrower than the legs 8and 9 and serve as shunt paths for the secondary flux as is well knownin the constant current transformer art. The ends of the legs 10 and 11may be provided with notches 14 to receive clamping bolts or rivets forholding the shunt laminations rigidly together. The laminations of boththe primary section 1 and the secondary or shaped sections are heldtogether in any well known manner as by bolts or rivets 15, and ifdesired the entire assembly may be filled with tar, asphaltum or otherinsulating com-- pound for preventing vibration of the laminations, andthe whole assembly may he enclosed in a suitable casing through whichthe bolts 15, if desired, may likewise pass to further clamp thelaminations together. As will be obvious from the drawing the shunts 10and 11 are positioned between the primary coil 2 and the associatedsecondary coils 4;.- and 5. Preferably the air gap 12 and the legs 10and 11 are so designed that as the secondary load increases acorresponding increase in the shunting effect of the magnetic linesoccurs through the legs 10 and 11' and.

across the said gaps. is not at all nece f;

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sary that the secondary core portions 7 be saturated to achieve this reulating efiect.

It will be obvious that t e reluctances of the shunt paths through thelegs 10 and 11 may be chosen in any desired ratio with res act to thereluctance of the main magnetic ux path so as to provide the desiredregwlating action. Suitable insulating strips 16 are provided, forinsulating the windings from the legs, 8, 9, 10 and 11 of the secondaryportion of the core.

Inasmuch as the magnetic shunt legs 10 and 11 are integrally formed aspart of the legs 7 it will be clear that the gaps 12 remain absolutelyconstant even though the laminations should be subjected to considerablevibration. Furthermore, the design of core as shown in the drawingenables the transformer to be easily and quickly assembled. Furthermore,once the length of the shunt legs 10 and 11 has been decided upon theshunt gaps 12 remain absolutely constant and no great care need be takenin assembling the core to insure the accuracy of these gaps since thegap is automatically determined by the len he of the legs 8 and 9 andthe le 10 an 11. All that is necessary in assem ling the transformer isto position the windings upon the primary core portion 1, and then toassemble the secondary core portions with the legs 8, 9 abutting againstthe core portion 1, after which the entire assembly may be rigidlclamped together as a unit.

is a further advantage of the particular design of core shown, thereluctanceof the main magnetic path may be easily controlled merely byinserting suitable members between the ends of the legs 8, 9 and thecore portion 1, although this latter feature is not absolutelynecessary. The-action of the magnetic shuntsin shunting the main fluxaway from the secondary windings 4 and 5 increases as the secondary loadcurrent increases, as will be understood by those skilled in the art.

While certain specific arrangements and illustration of parts is shownin the drawing,

it will be understood that the invention is not limited thereto, andthat various chan es and modifications may be made without eparting fromthe spirit and scope of the invention. Thus instead of positioning theprimary winding 2 between the secondary, the primary winding may be madein two or more sections symmetrically disposed on the core section 1with respect to the secondary winding which may take the place of theprimary windin 2'as shown in the drawing.

Furthermore the dimensions ofthe respective sections of the core areshown in the drawing as merely illustrative and it will be obvious tothose familiar with the art that the size of the core sections and theshunt sections will be chosen in accordance with the regulatingcharacteristics desired. Furthermore, while the drawing shows a main orprimary core section 1 and a plurality of secondary core sectionsdisposed on opposite sides of the section 1, it will be understood thata single secondary core section may be employed.

Similarly in the arrangement actually shown in the drawing it is notabmlutely necessary to rovide gaps on opposite sides of the core 1. 'lihus the shunt legs 10 and 11 and half of the secondary core may be ofthe same length as the legs 8 and 9 while the shunt legs 10 and 11 ofthe other section of the secondary core may be shorter, as shown in thedrawin thus providing only two gaps in lace oft e four gaps shown.

ther changes and modifications may be made without departing from thespirit and scope of the invention.

While in the foregoing description mention has been made of a primarywinding and a pair of secondary windings, it will be understood that thesecondary windings may be connected either in series or in multiple asdesired, to constitute separate coil sections of the same winding, andsimilarly while the primary winding 2 is shown in the drawing as asingle coil, it will be understood that this I winding may consist oftwo ormore coil sections connected in parallel or in series. In anyevent the arrangement of the coils or coil sections as shown in thedrawing provides a symmetrical and properly balanced ma netic structuresince the primary coil or coi s are symmetrically disposed with relationto the entire magnetic circuit, and also with relation to the secondarycoils.

What is claimed is:

1. In a constant current transformer a core structure comprising astraight primary core portion, a secondary core portion having a pair oflegs at opposite ends abuttin against said primary core portion, and aoreshortened leg intermediate the ends providing a gapped magnetic shuntbetween the primary and secondary core portions.

.2. In a constant current transformer, a core structure comprising astraight primary core portion, a secondary core portion having apair oflegs at opposite ends abutting against said primary core portion, and apair 0 foreshortened legs intermediate the ends providing a gappedmagnetic shunt between the primary and secondary core portions.

3. In a constant current transformer a primary magnetic core, a centralwindin a pair of lateral windings spaced apart rom said central windingon said primary core, a secondary core for completely enveloping saidcoils, said secondary core having main magnetic lefis abutting saidprimary core an integra y intermediate shunt legs disposed between thecentral winding and the lateral windings.

4. A transformer comprising in combination a laminated core bar havingat least two primary and secondary coils mounted thereon in end to endrelation, a laminatedyoke member having at least one intermediate leginterposed between the ends of said coils with the end of said leg inclose proximity to said first named bar but with an effective air gapbetween such parts and means for connecting the end le s of said yokesnugly in contact with said rst named oar.

5. A step-up transformer comprising in combination a laminated core'barhaving a primary coil and two secondary coils mounted thereon in end toend relation with the rimary coil located between the two secon arycoils in spaced relation thereto, a laminated olre member having twointermediate legs interposed between the ends ofthe primary coil and theadjacent ends of the secondary coils, and means for connecting the endlegs or said yoke snugly to said first named core bar.

6. A shell type of transformer compris-' snugly to said first named corebar.

7. In a transformer, the combination of a straight laminated core bar, aprimary coil mounted on said core bar, a secondary coil mounted on saidcore bar in end to end re lation to said primary coil, a. second lanai--nated core bar in spaced relation to said first named core bar andhaving at least one intermediate leg formed therewith extending betweensaid coils into close proximity to said first rfamed core bar but withan efiective air gap between the 1e and said first named core bar, andan en leg at each end of the device each formed with one of said spacedcore bars and extending into snug engage ment with the other one of saidcore bars.

8. In a transformer, the combination of a straight laminated core bar, aprimary coil mounted on said core bar, a secondar coil mounted on saidcore bar in end to en relation to said primary coil, a laminated yokemember having an intermediate leg terminatin adjacent said core bar toform an air gap t erewith and lying between the adjacent ends of saidcoils and a leg at each end of said yoke and extending into snugengagement with said core bar. 7

9. In a transformer, the combination of av straight laminated core bar,a primary coil mounted on said core bar, two secondary coils mounted onsaid core bar, one on each side of said prima' coil and in end to endrelation to said prlmary coil, a laminated yoke member havingintermediate legs terminatin adjacent said core bar to form air gaps anlying between'the adjacent ends of the primary and secondary coils and aleg at each end of said yoke and extending into snug engagement withsaid core bar, ad acent the outer ends of said secondary coils.

In testimony whereof we have hereunto set our hands on this 14th day ofFebruary A. n, 1931.

- OSCAR A. PEARSON.

CHESTER H. THORDARSON.

